Destination signs for buses and trains must be changeable according to the particular route of the vehicle and each sign must be capable of displaying a large number of different destination messages. The typical destination name requires many different alphanumeric characters and the sign must be changeable quickly from one name to another.
It is usual practice to display a route number (or "run number") with each destination name. The route number and the destination name can be combined and the entire message stored in memory and called up as needed for display.
An electronic display system which is admirably suited for a destination sign operating in the above described manner is disclosed in the U.S. Pat. No. 3,750,138 granted July 31, 1973 to Burgan et al. A bus system in a metropolitan area often uses the same destination name with many different route numbers. For example, the destination name "HOLLYWOOD AND VINE" may be used on many different buses, each of which proceeds to that destination by different routes with identifying route numbers such as 124, 235, 313 and so on. This results in many different messages all of which have the same destination name. Accordingly, each different message requires a separate memory location and a large memory capacity is required.
Destination names frequently are made up of more than one word and the full name includes a large number of alphanumeric characters. The number of characters will often exceed the number of character modules in the display device and hence the full name cannot be displayed at one time. According to the Burgan et al U.S. Pat. No. 3,750,138 cited above, a sequential display may be used. For this purpose the destination name is divided into plural words or "word units" with the successive word units of the name being displayed in time sequence on the same character modules of the display device. This is a highly advantageous in that it avoids the need for having an unduly long display device or, alternatively, having a display device with two or more rows of character modules.
It would be desirable to have a destination sign which can display the destination name and route number without requiring large memory capacity or a complex central processing unit for combining names and numbers. An object of this invention is to provide an electronic destination sign which overcomes certain disadvantages of the prior art in displaying destination messages which may comprise different route numbers with the same destination name. In general, it would be desirable to have an alphanumeric sign in which displays a large number of different messages each of which is made up of two or more parts with one part being generated by a manually actuable selector rather than being stored in memory.